Images of the World Trade Center site show patterns of materials with spectral
absorptions due to vibrational processes

The map on this page (Vibrational Figure 1) shows locations of materials with
vibrational absorption features commonly found in clays and other phyllosilicates
(like muscovite), carbonates, and water-bearing sulfates. Such minerals are
commonly found in building materials. For example, walls are often constructed
with a board containing gypsum, a sulfate. Gypsum has been identified in samples
from the WTC area (see sample analysis section). Muscovite, carbonates, and
other hydroxyl-bearing minerals have also been identified in the WTC samples
(see the Integration of Results section).

The debris contains common building materials, therefore, the map also shows
these materials in other buildings not associated with the World Trade Center
(WTC) collapse. While the minerals mapped in any one location may or may not
be associated with the WTC event, a pattern is seen that shows the distribution
of materials related to the WTC collapse. This pattern matches the pattern
from the ferric and ferrous absorption features map.

The spectral absorptions due to vibrational processes are normally diagnostic
of mineralogy or material type. The spectral signatures in the WTC debris are,
however, quite weak (see laboratory spectroscopy of field samples, below).
Because of their weak strength, and influences of the spectral signatures of
other materials, including organics, definitive identifications could not be
made in this case. Definitive identifications might be made on such samples
if the sensor had a higher signal to noise.

Both the iron maps, dust/debris maps, asbestiform mineralogy maps, and vibration
absorption maps show a pattern of materials suggesting asymmetric distributions
to the composition of the debris/dust.

Again, at any one location in the image, the mapped materials may be unrelated
to the WTC debris because they may be common building materials used in the
area. However, if a certain type of debris must be cleaned up, this and the
other maps indicate the locations to investigate on the ground where similar
compositions occur.